1. Field of the Invention
The present invention relates to a filler neck cap for automobiles or the like and, more particularly, to an improved safety plastic filler neck cap which is developed for the purpose of further increasing the stability in function, i.e., to control the torque during screwing and to prevent fuel leakage from the filler neck port caused by the separation of the cap upon receiving an impact, with respect to the known screw-type plastic cap precedingly proposed by U.S. Pat. No. 4,494,673 which has been assigned to the applicant of the present invention.
2. Description of the Prior Art
In the conventional filler neck caps for automobiles or the like, a screw body to be threadably fitted into the fuel supplying port is generally unitedly assembled with a cap being positioned on its operating side or on the side of a handgrip cover portion through a ratchet mechanism enabling them to favorably control the opening-closing torque. Usually, the screw body and the cap are made from different materials. In this connection, polyamide resin, etc. is ordinarily used for the cap and, on the contrary, polyacetal resin, etc. is often utilized for the screw body. This results from the requisites for the particular cap components; and they should, of course, be formed from optimum plastic materials. Generally speaking, oil resistance and water resistance are required for the screw body, whereas the cap should satisfy common essential properties, such as ready manipulation, weather-proofing, antishock and the like.
Then, polyamide resin which has been every so often used for the cap has a higher water absorption than polyacetal resin, etc. and, therefore, it entails problems concerning a lack of stability in dimension. Thus when the combination for the selected different plastic materials is chosen the safety filler neck cap, which includes the function controlling the torque during screwing it into the fuel supplying tube as well as the function preventing fuel leakage from the filler neck port caused by the separation of the cap upon receipt an impact force, the torque in screwing and the releasing action vary to cause the functions of the cap to become unstable due to seasonal variation in temperature and humidity. There exists a problem that each component in the cap has to be manufactured highly precisely within high parameters of accuracy for practical use. For the above reasons, an attempt has been made to substitute the materials used for the screw body and the cap with a common material such as polyacetal resin or the like having substantially no water absorption, but the latch and the latch teeth wear more rapidly than in the case of a combination of different materials. Thus, the life span of the cap is shortened; and the cap will produce a grating noise causing the user to feel uncomfortable. Although these defects have not been solved hitherto, it is the present procedure to apply a combination of different materials in the manufacturing.
In the conventional plastic filler neck cap, a measure taken to unitedly assemble the latches with the latch teeth provided interposingly between the cap and the screw body to control the clamping torque has been disclosed, for example, in U.S. Pat. No. 4,458,823 and U.S. Pat. No. 4,458,824. However, these patents have been developed mainly for the purpose of resolving conventional problems during the molding; thus the purposes of the patents do not reside in accomplishment of controlling the rotational torque by the substitution of material and of protecting the components from breakage by instantaneous separation upon receiving an impact force. The construction of the filler neck cap according to the present invention can be thus clearly differentiated from those disclosed in the patents.